OF FLORIDA CITRUS
OF FLORIDA CITRUS
JAMES E. BROGDON
FRED P. LAWRENCE
This circular is designed to help citrus growers become
better acquainted with citrus insects and mites and their
injuries. In addition, some beneficial ladybeetles and
several fungi are illustrated and discussed.
Purple mites (mites and eggs in circle are magnified 36 times).
The citrus red mite (purple mite, red spider), Metatetrany-
chus citri (McG.), is about 1/50 inch long, rose to deep purple
in color, and lays a round, reddish-colored egg. Eggs and mites
are found on both surfaces of the leaves and on fruit and green
wood. Eggs deposited on leaves are most abundant along midrib
and petiole. The mite seems to prefer the upper surface of the
leaf. Although prevalent throughout the year, they are more
numerous from November to April. The leaf injury, scratching
or etching as shown above, may result in the collapse of leaf
cells and leaf drop. Feeding injuries, noted on young fruits, do
not appear to affect grade. Examination for mites and eggs
should be made with the use of a hand lens.
AGRICULTURAL EXTENSION SERVICE
Top-Upper surface of leaf showing early six-spotted
Center-Injury to under side of leaf. (Mites and eggs
in circle magnified 36 times.)
Bottom-Upper surface of leaf showing severe six-
spotted mite injury. (Leaves are /. natural size.)
The six-spotted mite, Eotetranychus sexmaculatus
(Riley), is about 1/50 inch long, pale grayish-yellow in
color, and lays a round, yellowish-white egg. It usually
has six dark spots arranged in two rows along the abdo-
men. With a 10-power magnifying glass, the spots are
barely visible on the adult mites and few or none can
be seen on the young. Mites and eggs are found in colo-
nies, often covered with a webbing, and located on the
under surface of leaves only. Feeding injury results in
yellow or chlorotic areas, usually cupped toward the
upper surface, and subsequent leaf drop in many cases.
These mites may be numerous from December to May,
particularly after a cold December, and then disappear
with the occurrence of summer rains. Although grape-
fruit varieties are preferred, they can be found on other
types of citrus. Inspections should be made with the use
of a hand lens, although the yellow spotting can be seen
with the naked eye.
APHIDS, COTTONY CUSHION SCALE, LADYBEETLES
LEFT CENTER AND TOP-Aphids (magnified 10 times) and
aphid injury to young growth. Aphids, or plant lice, are par-
ticularly important on young trees. The green citrus or spirea
aphid, Aphis spireacola Patch., is the most common. Others,
including cotton or melon aphid, Aphis gossypii Glover, black
citrus aphid, Toxoptera aurantiae (Fonsc.), and green peach
aphid, Myzus persicae (Sulz.), are found at times. Ants feed on
a sweet, syrupy excretion of aphids and may move them around,
aiding in their spread. Aphids injure young tender growth in
the spring, especially Temples and tangerines, causing leaves
to curl. Inspect for these insects at regular intervals, beginning
when new growth starts.
TOP RIGHT-Cottony-cushion scale, Icerya purchase Mask.
(about twice natural size), is most damaging to young trees.
It is usually kept under control on citrus by the Vedalia or
Australian ladybeetle, Rodolia cardinalis (Muls.), shown feeding
on the scale. The large Vedalia ladybeetle is magnified 6 times.
BOTTOM ROW (all magnified 5 times)-Left to right: Twice-
stabbed ladybeetle, Chilocorus stigma (Say); ladybeetle larva;
convergent ladybeetle, Hippodamia convergens Guer.; blood-red
ladybeetle, Cycloneda sanguine (L.). Ladybeetle adults and lar-
vae feed on many citrus pests, including scales, aphids and mites.
TOP-Russeting of oranges (2A natural size) cai
citrus rust mites.
CENTER-Citrus rust mites, Phyllocoptruta oleivora (/
magnified 15 times. These mites are so small that tt
difficult to recognize under a 10-power magnifying glas,
are yellow and carrot- or wedge-shaped. (See further
sion of rust mites under photographs on back of this cir
BOTTOM-Greasy spot on upper surface of leaf (lef:
under surface of leaf (right) (about /2 natural size).
spot, formerly called greasy melanose, probably is a
and may cause leaf drop. At this writing the relate
between greasy spot and rust mites and purple mites
RUST MITES AND EGGS MAGNIFIED ABOUT
20 TO 25 TIMES
RUST MITES are so small (about 1/200 inch long) that they
cannot be recognized with the unaided eye. Under a 10-power
hand lens they appear as lemon-yellow, carrot- or wedge-
shaped objects, although distinct features cannot be seen. They
can be seen more easily on green leaves and fruits than on
ripe fruits. A heavily infested leaf appears to be fuzzy or dusty.
They are often confused with eggs of the citrus whitefly. All
rust mites are capable of laying eggs and the life cycle requires
only about a week in summer, which accounts for the rapid
build-up often noted.
RUST MITES infest leaves, fruit and tender green shoots, caus-
ing russeted or rusty colored fruit. Heavily infested leaves lose
their gloss and dark-green color and may drop prematurely.
Infestations may develop on the leaves just before the trees
bloom and cause injury to young fruits soon after they are
set. Rust mites seem to prefer more exposed locations and are
numerous in the tops of trees. They are more numerous on
fruit from spring to late summer. Inspect the fruits and under
surface of leaves with a hand lens.
MELANOSE, a fungus disease, causes blemishes on citrus fruit
often confused with russeting or rust mite injury. Lesions
caused by the melanose fungus are blacker, more rounded and
RUST MITE AND EGGS GREATLY MAGNIFIED
raised and have a rough or sandpapery feel. Scab, another
fungus problem, causes spots that are usually rougher, larger,
more irregular and lighter in color than rust mite injury.
.4 111. ,
MEALYBUGS MAGNIFIED APPROXIMATELY 5 TIMES
THE CITRUS MEALYBUG, Pseudococcus citri (Risso), derives its
name from the mass of mealy wax with which it covers itself
and its eggs. Females grow to a length of 1/10 to 1/4 inch
and lay eggs in the mass of cotton which they secrete. They
give off large amounts of honeydew in which sooty mold
fungus (see other side of the circular) develops, blackening the
colony and surrounding vegetation. They may get into bark
crevices of limbs and the trunk and in such sheltered places
as the angle between the petiole of the leaf and stem. Mealy-
bugs often collect around the stem end of the fruit (especially
grapefruit) and cause fruit drop. Controls should be applied
before mealybugs have settled under the fruit calyx. Another
favorite place for mealybugs is the sheltered area formed by
clusters of two or more fruits, particularly grapefruit. Mealy-
bugs often are confused with cottony-cushion scale.
MEALYBUGS (NATURAL SIZE) ON FRUIT
SOFT BROWN SCALE (ABOUT NATURAL SIZE)
TOP-Soft brown scale, Coccus hesperidum (L.), is la
and thicker than armored scales. Adult females are betv
1/8 and 1/6 inch lorig, oval in outline, dark in color, swo
in the center and flat at the margins. Eggs hatch within
mother scale. Crawlers are yellow and nearly transpar
Young nymphs attack only young growth, leaves and tv
Consequently, this scale increases most rapidly during flush
growth in spring and early summer. Sooty mold fungus
velops on the sweet, syrupy excretion of these scales.
brown scales are highly parasitized by several wasp-
insects and generally do not build up to heavy infestat
unless the parasites are reduced from some cause.
BELOW-Florida wax scale, Ceroplastes floridensis Coi
is a soft scale that is white when not stained by- sooty r
or other foreign matter and often has a pinkish tint.
adult female is 1/8 inch or less in length, oval in ger
outline but presenting an angular appearance due to d(
shaped masses of wax on the back. The pale-brown cral
show a preference for leaves and collect especially along
midrib on the under side. Young larvae are star-shaped.
scale is highly parasitized and is of minor importance
Florida in citrus groves.
FLORIDA WAX SCALE (MAGNIFIED 5 TIMES)
NGE DOG BUTTERFLY, Papilio cresphontes Cram.
ORANGE DOG is a caterpillar that feeds greedily on
Two or three may entirely defoliate a young tree in
days. They are most important on young trees and
stock. The caterpillar is dark-brown with light-yellow
growing to a length of 2Y2 inches. The front part of
y is enlarged and, when not feeding, the caterpillar
e head back into these large segments and causes the
front part of the body to resemble, somewhat, the head
og, hence the name. The orange dog can push out a
skin back of the head which forms two long, red,
e projections. This organ gives off a strong, disagreeable
which repels natural enemies. The adult is a large, yellow
ORANGE DOG ON LEAF
DIDS are about the same color as leaves, which makes
difficult to see. Eggs are usually laid in rows on twigs and
reargins of leaves. A large percentage of most egg
show holes made when a wasp-like insect parasite
es from them. Katydids sometimes feed on the rind of
growing oranges, causing large, smooth, sunken areas which
develop with the fruit. They consume some plant foliage but
are considered to be minor pests of citrus.
A KATYDID ADULT
EGGS OF THE BROAD-WINGED KATYDID,
Crytophyllus concavus (not illustrated)
OTHER PESTS OF CITRUS
CHAFF SCALE, Parlatoria pergandii Comst., often is a major
pest of citrus, especially tangerines. The scales are thin, gray or
brownish-gray and often completely cover branches. They over-
lap each other, giving the tree an appearance of being covered
with chaff. It is partial to smaller branches and trunks of small
trees, although it will attack leaves and fruit. The scales cause
green spots on the rind of fruit that are not removed in the
Several species of ANTS are found in citrus groves. Some may
cause injury to newly-budded trees in the nursery; others are
a nuisance to pickers. Ants may damage the trees indirectly by
protecting and caring for scale-insects, aphids and especially
mealybugs. Ants carry them from place to place and feed on
the ,excreted sweet, syrupy honeydew.
PLANT BUGS, or stink bugs, puncture the rind of fruit, often
causing them to drop. Several kinds are found in groves, but
the most common and destructive is the Southern green stink
bug, Nezara viridula L. The pods of leguminous cover crops,
such as beggarweed and crotalaria, are attractive to this insect
and often induce increased infestations.
Several species of GRASSHOPPERS may be found in citrus
groves, causing injury to fruit and foliage. Eggs are laid in the
ground and after hatching, young nymphs may migrate to the
cover crop and trees in the grove.
The PINK SCAVENGER WORM, Pyroderces rileyi
small caterpillar with a deep wine red abdomen
head and black mouth parts. It has a dark broi
behind the head. The insects feed primarily on de
ing areas of fruit but also feed on the rind of
causing a lowering of grade. They may be present I
infestations of mealybugs, and are sometimes nu
heavy infestations of purple scale on fruit.
BLACK SCALE, Saissetia oleae (Bern.), is a sof
although widely distributed in Florida, is only a n
citrus. The adult female is 1/8 to 1/4 inch long
dark brown in color. It is nearly hemispherical in
markings on the back that form a distinct "H".
prefer leaves but migrate to stems before they are
They may infest leaves, bark and fruit. This scale is
importance in California and some other citrus-proi
tries, but usually is kept in check in Florida b3
LONG SCALE, or Glover scale, Lepidosaphes glov
is not as important in citrus now as in past year!
similar to purple scale,, but is straighter and much
TERMITES, commonly called white ants or wooc
times damage citrus trees, especially young trees
cold protection. If banking soil contains cellulose rr
as roots, chips and paper bags, termites may
material and later injure young trees.
CITRUS SNOW SCALE, Unaspis citri (Comst.), g
from the white color of male scales. Female scales
blackish. Like chaff scale, they infest chiefly the br;
show a preference for larger branches and are oft
trunks. The scales may drain the sap from the b
it to die and split. They are minor pests of cit
areas, but are important in localized areas, such
Since new pesticides are constantly being introd
tempt is made here to list specific recommendation
cides and miticides. Commercial growers should
Better Fruits Program Spray and Dust Schedule, w
of dooryard citrus may refer to Agricultural Exten
Circular 139, Control of Insects and Diseases c
Citrus Trees. These circulars may be obtained from
agricultural agent or by writing to the Agricultur;
Service, University of Florida, Gainesville.
Appreciation is expressed to Marion Ruff Sheel
color illustrations, to the USDA for photographs
and 10, to Milledge Murphey, Jr., for photographs
9, to M. W. Tyler for photograph 2, to Louis W.
Milledge Murphey, Jr., College of Agriculture,
Joiner, Agricultural Extension Service, and A.
Agricultural Experiment Station, University of Flori
ville, for helpful suggestions in the preparation of tl
Helpful information was taken from Agricultural
Service Bulletin 88, Citrus Insects and Their Cont
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida, Flori
University and United States Department of Agriculture, Cc
H. G. Clayton, Director
PIT':LIES, SOOTY MOLD, WHITEFLY FUNGI
ST (enlarged 10 times)-Cloudy-winged whiteflies,
es citrifolia (Morg.), with immatures and dark-
eg s- Light-colored eggs are those of the citrus whitefly,
,es citri (Ashmn.), and are often confused with citrus
:Q C)ther whiteflies of lesser importance occur on citrus.
t da of whiteflies occur about March-April, June-July
;t -Sooty mold fungus, Meliola spp., develops on
1 Y syrupy excretions primarily of immature whiteflies,
o -'sser extent of aphids, mealybugs and certain soft
,Or it-ol of these insects will prevent the development
a" lRed Aschersonia (left), Aschersonia aleyrodis
ak-T brown whitefly fungus (right), Aegerita webberi
"ft neficial fungi that kill immature whiteflies. The
ar mistaken for Florida red scale. (Both V2 natural
FLORIDA RED SCALE, PURPLE SCALE
(Scales in circles are magnified 6 times,
those on leaves and twig are natural size.)
TOP-Florida red scale, Chrysomphalus aonidum (L.). Bright
yellow eggs are laid under the armor of the adult and produce
bright, lemon-yellow, oval-shaped crawlers. The adult female
is circular in outline, about 1/12 inch in diameter, and dark
reddish-brown in color, with a conspicuous reddish center.
There are usually four generations per year. These scales feed
on leaves and fruit, preferring exposed surfaces; particularly in
the tops of trees. Their feeding results in yellow areas on leaves
and fruit which may often be followed by extremely heavy leaf
and fruit dr.rpp, The denuded branches may be killed the
following fall and winter. Inspections of groves should be made
at intervals, particularly from May through October.
BOTTOM-Purple scale, Lepidosaphes beckii (Newm.), is the
most destructive insect in Florida citrus groves. Grayish-colored
eggs are laid in a sac-like enclosure under the armor of the
female. Crawlers are oval and have an off-white color with a
posterior brown tip. The mature female is purplish-brown in
color, about 1/8 inch in length and shaped somewhat like an
oyster shell. Peaks of the young stages occur in March-April,
June-July, and September-October. These scales feed on leaves,
fruit and wood and prefer shaded portions of the tree. Residues
of any type encourage heavier infestations. Yellow, chlorotic
areas on the leaf result in defoliation and subsequent twig
death. Infestations on the fruit, particularly near the stem end,
cause fruit loss, as well as green spots which can not be removed in
the coloring room. Inspections of groves should be made at inter-